This invention relates to lubrication of a bearing mounted around a vertical rotatable shaft in machines such as centrifugal pumps, engines, drill motors, and the like. The invention includes a reservoir for holding lubricant, means for withdrawing lubricant from the reservoir and for pumping the withdrawn lubricant to the bearing, a stator, and a passageway for communicating lubricant withdrawn by the withdrawing means to the bearing. The withdrawing means includes a rotor connected to the shaft. The stator, while encircling the rotor and extending axially into the reservoir, minimizes vortexing and churning of the lubricant by the rotor.
It is well known to use enclosed lubrication systems to lift lubricant to a vertically mounted bearing using a rotating inverted cone or flinger or using a wick. Inverted cones, screws or flingers pump lubricant from a reservoir while wicks remove lubricant from the reservoir by capillary action. These lubricating systems are not completely satisfactorily for high speed machines, i.e., 3550 RPM or more. When vertically pumping hot liquids using a pump, there is a tendency for heat to rise and be transported through the vertical shaft and bearing bracket into the lubricant and the bearing. For those machines that include a plurality of bearing sets having a common lubricant reservoir, heat is transported from one bearing set to another by the lubricant. A lubrication system must not only deliver an adequate amount of lubricant to minimize wear of the bearing but also be capable of providing a maximum amount of cooling of the bearing without generating an excessive amount of heat. A lubrication system must be as efficient as possible without generating excessive heat. Lubrication systems using inverted cone, screw, or flinger type pumps may be efficient but normally generate excessive heat. They generate heat because of churning and vortexing of the lubricant caused by the spinning action of the cone or flinger slicing through the lubricant in the reservoir. Churning results when the lubricant is sheared and agitated such as when an impeller, a vaned device or a cone is forced through the lubricant. This creates heat because of internal shearing of the lubricant molecules and also tends to degrade the lubricant because of emulsification. Vortexing (spinning of the lubricant) creates heat as a result of internal shearing of the outer boundary layer of lubricant in the reservoir and friction between the wall of the reservoir and the lubricant. Wicks are too inefficient to deliver sufficient lubricant for high speed machines.
Accordingly, there remains a long felt need for an improved lubrication system that is efficient and does not add heat to the lubricant. The system must include a lubricant pump that minimizes churning and vortexing when withdrawing lubricant from a lubricant reservoir.